It's possible they're just using the word in its proper sense (like in the movie The Parallax View), but since it's a DC property, so maybe. Or maybe it's more like an easter egg. Didn't someone say Ferris Air is a thing in Supergirl?

Whoa, that's a pretty big one. If it's the title of the episode, I doubt it's just an easter egg. My guess is that it possesses someone. Having a GL on would be too big of a thing not to have announced already (but I could be wrong). But an episode with the fear bug possessing people sounds right up Supergirl's alley.

"I think their main premise is that fear itself is a villain and can hope conquer it? Supergirl stands for hope, so we'll see. I think fear is her biggest opponent yet because it's more of a wildfire-type emotion."

I think if/when they do a DCW Crisis on Infinite Earths and merge the worlds it won't matter what show they're on... but I know Ferris Air AND Coast City were mentioned in Flash.

Benoist mentioning that it's like wildfire, makes me think the Fear Bug will make an appearance, but it'll be more about creating fear on a massive scale amongst people. (and yeah, there will be someone to punch .... can't imagine they'll have someone who looks like Hal, but you never know)